151.What are the types of fan? What is difference and give examples for their application?

Axial and Radial fan. Axial fan can provide large flow at low head. Ex. FD fan, Ignitor fan, ID  Fan, etc Radial Fan  can provide less quantity at high pressure. PA fan, Flame scanner cooling air fan, etc

150.How to control flow of fan?

By modulating the inlet vane

149.How to control process flow for centrifugal pump and positive displacement pump?

Centrifugal pump - Modulating the discharge side valve.

Positive displacement pump - Modulating  recirculation valve.

148.What are the type of pumps and give their typical example?

Positive displacement, reciprocating, centrifugal type, etc. Positive displacement type - Fuel oil pumps, Reciprocating Type - Chemical dosing pump, Centrifugal type - Feed water pump and other general service pumps.